Part of: #14522
⚠️ Depends on #14690 ⚠️

Description

This PR caches the saved packages received from remote after saving (starring) a package, so we can fetch those saved packages from storage during Woo Shipping label creation:

• Updates WooShippingStore.createPackage(siteID:customPackage:predefinedOption:completion:) to upsert the response received from remote:
  • Adds methods to upsert WooShippingCreatePackageResponse in the background by handling the custom packages and saved predefined package IDs in that response.
  • Updates the methods that upsert custom packages and saved predefined packages, so they take those package arrays as parameters instead of a complete packages response. This way we can reuse those storage methods when we receive a WooShippingCreatePackageResponse.
  • Adds a method to transform the saved predefined package IDs into saved packages for storage. (This uses the logic from WooShippingAddPackageViewModel, where we were previously doing this transformation.)

Testing information

Confirm unit tests pass. You can also confirm the packages response continues to work as expected:

1. Install and set up the Woo Shipping extension on your store.
2. Build and run the app with the revampedShippingLabelCreation feature flag enabled.
3. Create an order with the processing status and at least one physical product.
4. In your WooCommerce product settings on the web, change the weight and dimension units and save your changes.
5. On the Orders tab in the app, open the order you created.
6. In the order details, select "Create Shipping Label."
7. Immediately tap "Select a Package."
8. Select the Saved tab and confirm the expected packages appear.

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Reviewer (or Author, in the case of optional code reviews):

Please make sure these conditions are met before approving the PR, or request changes if the PR needs improvement:

• The PR is small and has a clear, single focus, or a valid explanation is provided in the description. If needed, please request to split it into smaller PRs.
• Ensure Adequate Unit Test Coverage: The changes are reasonably covered by unit tests or an explanation is provided in the PR description.
• Manual Testing: The author listed all the tests they ran, including smoke tests when needed (e.g., for refactorings). The reviewer confirmed that the PR works as expected on all devices (phone/tablet) and no regressions are added.